Nuclear reactor spacer grid and ductless core component

Abstract

The invention relates to a nuclear reactor spacer grid member for use in a liquid cooled nuclear reactor and to a ductless core component employing a plurality of these spacer grid members. The spacer grid member is of the egg-shell type and is constructed so that the walls of the cell members of the grid member are formed of a single thickness of metal to avoid tolerance problems. Within each cell member is a hydraulic spring which laterally constrains the nuclear material bearing rod which passes through each cell member against a hardstop in response to coolant flow through the cell member. This hydraulic spring is also suitable for use in a water cooled nuclear reactor. A core component constructed of, among other components, a plurality of these spacer grid members, avoids the use of a full length duct by providing spacer sleeves about the sodium tubes passing through the spacer grid members at locations between the grid members, thereby maintaining a predetermined space between adjacent grid members.

We claim: 
     
       1. A ductless core component for use in a liquid cooled, fast flux nuclear reactor core for axially and laterally constraining a plurality of elongated rods containing nuclear material comprising: an upper support plate member,   an upper spacer grid member,   a plurality of intermediate spacer grid members,   a lower spacer grid member,   a lower support plate member,   a nozzle means,   a flow dispersion tube means for fluidly and mechanically connecting said nozzle means to said lower support plate member,   a handling socket means attached to said upper support plate member for enabling gripping of the core component,   a plurality of orifice plates disposed between said lower support plate member and said nozzle means,   a plurality of support rods passing through said lower spacer grid member, said intermediate spacer grid members, and said upper spacer grid member fixedly attached to said lower support plate member and to said upper support plate member, said support rods being provided with passage means axially therethrough for passing a flow of coolant, and   a plurality of spacer sleeve means disposed about each of said support rods between said upper spacer grid member and the uppermost of said intermediate spacer grid members, between each of said intermediate spacer grid members and said intermediate spacer grid member immediately beneath it, and between the lowermost of said intermediate spacer grid members and said lower space grid member for maintaining a predetermined spacing between said grid members between which said spacer sleeve means are disposed, each of said spacer sleeves being bowed with respect to their axis to grip said support rods to prevent flow induced vibration damage to said support rods,   each of said upper spacer grid member, said plurality of intermediate spacer grid members, and said lower spacer grid member comprising a plurality a cell members, the cell members being substantially triangular and being formed through the interconnection of a plurality of top grid strip members, a plurality of middle grid strip members, a plurality of bottom grid strip members, and outer grid strip members, each elongated rod passing through and being laterally constrained within one of the cell members, each cell member comprising three wall members, each wall member comprising a portion of a top grid strip member, a middle grid strip member, a bottom grid strip member, or an outer grid strip member.   
     
     
       2. The ductless core component according to claim 1 wherein each wall member of each cell member formed by interconnecting the top grid strip members, the middle grid strip members, the bottom grid strip members, and the outer grid strip members consists of a portion of a top grid strip member, a middle grid strip member, a bottom grid strip member, or an outer grid strip member. 
     
     
       3. The ductless core component according to claim 1, futher comprising hardstop members provided intermediate two of the wall members of each substantially triangular cell members and spring means provided intermediate a third wall member of each cell member for biasing an elongated rod passing through the cell member against the hardstop members. 
     
     
       4. The ductless core component according to claim 3, wherein said spring means is disposed at an angle with respect to the flow of coolant through the ductless core component, which flow is substantially along the axis of the elongated rods, which axis corresponds to the axis of the ductless core component, and is resilient, whereby the flow of coolant upwardly through the cell member causes a biasing force in said spring means, the biasing force forcing the rod against said hardstop members, the strength of the biasing force being dependent on the rate of flow of coolant through the nuclear reactor core component. 
     
     
       5. The ductless core component according to claim 1 wherein the top grid strip members are provided with first slot means along the bottom edges thereof for receiving middle grid strip members, the middle grid strip members are provided with the second slot means along the top edges thereof for engaging said second slot means of the top grid strip members when the top grid strip members and the middle grid strip members are interconnected, the middle grid strip members being further provided with the third slot means along the bottom edges thereof for receiving bottom grid strip members, and the bottom grid strip members are provided with third slot means along the top edges thereof for engaging the third slot means when the middle grid strip members and the bottom grid strip members are interconnected. 
     
     
       6. The ductless core component according to claim 5 wherein the outer grid strip member of each of said top, intermediate and lower spacer grid members is adapted to engage the lateral edges of the top grid strip members, the middle grid strip members and the bottom grid strip members interconnected to form each top, intermediate, and bottom grid member.